1. Field of the Invention
The present invention relates to backlight units, and more particularly, to a backlight unit for improving light efficiency, and a liquid crystal display device including the backlight unit.
2. Description of the Related Art
A liquid crystal display (“LCD”) device has gradually extended its application range due to light weight, thin thickness, and low consumption power driving. The LCD device applies an electric field to liquid crystal materials with dielectric anisotropy, injected between two substrates, and controls the amount of light transmitted into the substrates by adjusting the intensity of the electric field, thereby displaying a desired image.
Since an LCD panel of the LCD device is a non-luminous element that cannot emit light by itself, the LCD device includes a backlight unit for providing light to the LCD panel.
A light emitting diode (“LED”) used for the backlight unit has long life span, fast lighting speed, low power consumption and high impact resistance, compared to a cold cathode fluorescent lamp (“CCFL”), etc. Moreover, the LED is suitable to make the backlight unit relatively small and thin.
Such LEDs are mounted on a light source substrate supplying driving voltage to the LEDs. The light source substrate may be bonded to a light guide plate for guiding an incident light from the LEDs toward an LCD panel. FIG. 1 is a plan view illustrating a light guide plate and LEDs of a conventional LCD device of the prior art. Maximum light efficiency can be obtained when emitting surfaces of LEDs 16 are in contact with an incident surface of a light guide plate 24 as illustrated in FIG. 1. However, lights emitted from the LEDs 16 overlap each other in areas “A” where a portion of the light guide plate 24 does not overlap the LEDs 16. A “hot spot” phenomenon occurs in that the areas “A”, where the light emitted from the LEDs 16 overlap each other, include a greater amount of emitting lights than the other areas and thus seem to be relatively bright.